1. Field of the Invention
The present invention relates to a toner that is used in image-forming methods such as an electrophotographic method, an electrostatic recording method, and a toner jet method.
2. Description of the Related Art
There has been demand in recent years for higher speeds and lower power consumption in printers and copiers, and this has required the development of toners in which the low-temperature fixability co-exists in good balance with the heat-resistant storability.
In response to this, various investigations have been carried out into toners that use a crystalline resin-containing binder resin. A crystalline resin exhibits a high viscoelasticity, as a solid, in the temperature range below its melting point, but exhibits a sharp drop in its viscoelasticity when its melting point is exceeded, and as a consequence it can be expected that, through the utilization of this property, co-existence between the heat-resistant storability and low-temperature fixability can be brought about.
However, in actuality the crystallinity of the crystalline resin undergoes a decline in a toner that uses a crystalline resin-containing binder resin. The not fully crystallized fraction of the crystalline resin then plasticizes the binder resin, which has caused the problem of a deterioration in the heat-resistant storability.
In response to this, inventions have been introduced—in Japanese Patent Application Laid-open Nos. 2006-113473 and 2011-141489—that, through the addition of a crystal nucleating agent to the crystalline resin-containing binder resin, bring about an improvement in the heat-resistant storability by inhibiting the decline in the crystallinity of the crystalline resin.
While these inventions do bring about an inhibition of the decline in crystallinity and thus bring about an improvement in the heat-resistant storability, there is a tendency, when crystallization of the crystalline resin has been promoted with a crystal nucleating agent, for the crystals produced in the toner to exhibit an uneven distribution. When they end up being unevenly distributed toward the interior of the toner, the low-temperature fixability is then reduced; when they end up being unevenly distributed to the toner surface, the charging performance and the durability are then reduced.